1. Field of the Invention
The present invention relates to a wireless communication apparatus, and in particular relates to a configuration mounting a high-frequency coupler on a wireless communication apparatus.
2. Description of the Related Art
Standards for wireless communication include wireless LAN such as IEEE802.11 or Bluetooth (Registered Trademark). These techniques propagate electrical waves into space using a radiation electric field that is generated from an antenna to thereby enable communication between apparatuses.
By contrast a communication method, such as radio frequency identification (RFID), has been proposed that uses an electrostatic field or an induction field in substitution for a radiation electric field. This communication method communicates with a low-frequency signal using an electrical field coupling method or an electromagnetic induction method. Since this communication method communicates using a low-frequency signal, the communication speed is slow, and therefore large-capacity data communication is difficult.
In contrast to conventional RFID, a close proximity wireless communication system that enables large-capacity data communication or a configuration of a high-frequency coupler used for such a system has been proposed. Such a system uses an electrical field coupling method, an electromagnetic induction method, or an induction field method caused by an electrostatic coupling method to thereby transmit high-frequency and wide-band signals (for example, refer to U.S. Pat. No. 7,750,851 (Japanese Patent Application Laid-Open No. 2008-154198) or US 2008/0076351 (Japanese Patent Application Laid-Open No. 2008-271606)).
Furthermore a communication apparatus design or an arrangement between a transmitter and receiver has been proposed to expand the distance between the coupling electrodes of a transmitter and receiver by electrical field coupling (for example, US 2008/0153416 (Japanese Patent Application Laid-Open No. 2008-271605, Japanese Patent Application Laid-Open No. 2008-099235), US 2008/0076351 (Japanese Patent Application Laid-Open No. 2008-099236)).
In an close proximity wireless communication system as described above, data communication is performed between a transmitter and a receiver via a high-frequency coupler that includes a coupling electrode configured as a flat plate. Even when the transmitter and the receiver are disposed in close proximity, unless the coupling electrodes of the transmitting side and the receiving side are opposed to each other and the coupling electrodes are superimposed to some extent, there is a considerable deterioration in transmission characteristics. Furthermore, when the coupling electrode of the receiver facing the transmitter is assumed to be positioned at a plurality of positions for example, a plurality of coupling electrodes must be provided on the transmitter in correspondingly opposing positions.